Castilleja hidalgensis is described from several collections from xeric limestone sites in central Hidalgo, Mexico. The new species belongs to a small complex of poorly known and uncommon species within sect. Euchroma, sharing important characteristics with C. macrostigma, the first-described taxon in this assemblage. The new species appears to be rare and highly restricted both geographically and ecologically. A key to the species of the C. macrostigma group is provided.